publishDir compatibility with Azure Blob Storage

Bug report

Expected behavior and actual behavior

Expected behavior is that publishDir directive should work with Azure links, using different formats.
Actual behavior is that publishDir fails for:

• Azure links starting with https://
• or Azure links with paths containing the storage account az://<storage-account>.<bucket>

Steps to reproduce the problem

• set up Nextflow with Azure Cloud (basic set up)
• run the nf-canary pipeline
• pass in differently formatted paths for params.outdir

Working example:

nextflow run https://github.com/seqeralabs/nf-canary -r main -w az://nf-scratch/work --outdir "az://test-public" # succeeds

Failing example1 - storage account in the path:

nextflow run https://github.com/seqeralabs/nf-canary -r main -w az://nf-scratch/work --outdir "az://nfazurestore.test-public" # fail
ERROR ~ Error executing process > 'NF_CANARY:TEST_PUBLISH_FOLDER'

Caused by:
  /nfazurestore.test-public: Unable to determine if root directory exists

Failing example 2 - https path used:

nextflow run https://github.com/seqeralabs/nf-canary -r main -w az://nf-scratch/work --outdir "https://nfazurestore.blob.core.windows.net/test-public" # fail
ERROR ~ Error executing process > 'NF_CANARY:TEST_PUBLISH_FOLDER'

Caused by:
  Create directory not supported by HTTPS file system provider

Root cause of failures is:

• first in FileHelper.groovy paths get transformed into canonicalPath (for example into /<storage-acccount>.<bucket>)
• then Files.createDirectories(this.path) fails with the given error message

Environment

• Nextflow version: 23.12.0-edge build 5901
• Java version: openjdk 21.0.1 2023-10-17 LTS
• Operating system: macOS Sonoma - 14.2.1 (23C71)
• Bash version: zsh 5.9 (x86_64-apple-darwin23.0)

Additional context

Reasoning for path with storage account name included support:
Azure bucket/container names are not unique, they are only unique in a storage account. So to be able to identify them correctly, in Seqera Platform the following path format is used az://<storage-acccount>.<bucket>. Because Nextflow has knowledge of the storage account name - it has to be set up in the config - this part could be easily removed from the path, fixing the issue.

Reasoning for path with https support:
Azure docs about referencing blobs suggest using an URL like this: https://<storage-acccount>.blob.core.windows.net/<bucket>.

Start with FileHelper.groovy and reproduce the failure using the nf-canary commands and the three outdir formats described in the issue. Trace where paths become canonicalPath before directory creation. Done means publishDir works for az://bucket, az://., and the documented Azure HTTPS URL format.